Belt conveyor systems are used in many different applications to transport material from one place to another. In reprographic apparatuses such as printers and copiers, belt conveyor systems are used to convey sheets of receiving material through the apparatus. For example, from a sheet input tray to a transfer roll, from a transfer role to a fuser, from a fuser to a finishing device such as a stapler or a folder, and from a finishing device to an output tray.
One type of belt used in reprographic apparatuses is a mesh belt that is held under tension between two or more rollers. At least one roller is driven to rotate the belt. The belt runs over a vacuum plate which is a perforated plate that forms the side of a vacuum box. In the vacuum box a partial vacuum is kept. This partial vacuum forces air outside the box to be sucked through the mesh belt and the perforations into the box. A sheet positioned on the mesh belt is therewith sucked against the mesh belt and moved with the moving belt moving the sheet from a first point to a second point.
In belt conveyor systems in general, it is known to provide the belt near the edges with markings to create an alternating pattern near the edge. The pattern makes it possible to determine the belt velocity. It is further known to determine an inclination of the belt by calculating a difference in belt velocity between the two edges.
It is not obvious though to determine a lateral belt position from the inclination of the belt.
When applying mesh belts, it is known to weave a pattern into the mesh fabric by alternating high density weave areas with low density weave areas. Monitoring the pattern during operation enables the determination of the lateral position of the belt.
The problem with a mesh comprising high density areas and low density areas is that this leads to non-uniform properties of the belt across its surface. In for example a sheet conveyor system in a reprographic apparatus this may lead to ripples and even creases in the sheets being conveyed, resulting in poor image reproduction quality or even jams in the sheet conveyor system.
It is an object of the present invention to provide a belt conveyor system with lateral position detection with the disadvantages of the prior art at least mitigated.